This project seeks to clarify several aspects of the interactions of immunoglobulins both with respect to their specific reactivity as antibody and with respect to the light chain-heavy chain interaction. In the first area experiments will be designed to evaluate quantitatively the energetic significance of the bivalence of antibody and to relate this information to the interaction of antibody with particulate antigens, such as viruses and cells. Direct evidence for the existence of cell-bound antibody will be sought and attempts made to solubilize it for biochemical characterization. Finally, separated light and heavy chain populations will be prepared in their native state and the interactions between them studied from the energetic and conformational points of view. Our efforts will be directed towards understanding the aspects of this interaction associated with clonal specificity.